fix Python version detection bug (#1246)

* fix Python version detection bug

* Update setup_venv.ps1

setup_venv.ps1

@@ -45,7 +45,7 @@ if ($arguments -eq "--force"){
         Remove-Item .\shark.venv -Force -Recurse
         if (Test-Path .\shark.venv\) {
             Write-Host 'could not remove .\shark-venv - please try running ".\setup_venv.ps1 --force" again!'
-            break
+            exit 1
         }
     }
 }
@@ -78,12 +78,12 @@ if (!($PyVer.length -ne 0)) {$p} # return Python --version String if py.exe is u
 if (!($PyVer -like "*3.11*") -and !($p -like "*3.11*")) # if 3.11 is not in any list
 {
     Write-Host "Please install Python 3.11 and try again"
-    break
+    exit 34
 }
 
 Write-Host "Installing Build Dependencies"
 # make sure we really use 3.11 from list, even if it's not the default.
-if (!($PyVer.length -ne 0)) {py -3.11 -m venv .\shark.venv\}
+if ($NULL -ne $PyVer) {py -3.11 -m venv .\shark.venv\}
 else {python -m venv .\shark.venv\}
 .\shark.venv\Scripts\activate
 python -m pip install --upgrade pip